4 A piston can slide inside a tube which is closed at one end and encloses a quantity of gas (see Fig. 4).
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{30d0d728-d6d6-4a54-baf9-a6df8646bf64-2_154_1003_1080_571}
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\caption{Fig. 4}
\end{figure}
The pressure of the gas in atmospheric units is given by \(p = \frac { 100 } { x }\), where \(x \mathrm {~cm}\) is the distance of the piston from the closed end. At a certain moment, \(x = 50\), and the piston is being pulled away from the closed end at 10 cm per minute. At what rate is the pressure changing at that time?